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Subject[RFC][PATCH -mm 2/3] PM: Disable usermode helper before hibernation/suspend
Date
From: Rafael J. Wysocki <rjw@sisk.pl>

Use a hibernation and suspend notifier to disable the user mode helper before
a hibernation/suspend and enable it after the operation.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

kernel/kmod.c | 31 +++++++++++++++++++++++++++++--
1 file changed, 29 insertions(+), 2 deletions(-)
Index: linux-2.6.22-rc3/kernel/kmod.c
===================================================================
--- linux-2.6.22-rc3.orig/kernel/kmod.c 2007-05-27 18:56:44.000000000 +0200
+++ linux-2.6.22-rc3/kernel/kmod.c 2007-05-27 19:43:35.000000000 +0200
@@ -33,6 +33,8 @@
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/resource.h>
+#include <linux/notifier.h>
+#include <linux/suspend.h>
#include <asm/uaccess.h>

extern int max_threads;
@@ -46,6 +48,14 @@ static struct workqueue_struct *khelper_
*/
char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe";

+/*
+ * If set, both call_usermodehelper_keys() and call_usermodehelper_pipe() exit
+ * immediately returning -EBUSY. Used for preventing user land processes from
+ * being created after the user land has been frozen during a system-wide
+ * hibernation or suspend operation.
+ */
+static int usermodehelper_disabled;
+
/**
* request_module - try to load a kernel module
* @fmt: printf style format string for the name of the module
@@ -251,6 +261,22 @@ static void __call_usermodehelper(struct
complete(sub_info->complete);
}

+static int usermodehelper_pm_callback(struct notifier_block *nfb,
+ unsigned long action,
+ void *ignored)
+{
+ switch (action) {
+ case PM_PRE_FREEZE:
+ usermodehelper_disabled = 1;
+ return NOTIFY_OK;
+ case PM_POST_THAW:
+ usermodehelper_disabled = 0;
+ return NOTIFY_OK;
+ }
+
+ return NOTIFY_DONE;
+}
+
/**
* call_usermodehelper_keys - start a usermode application
* @path: pathname for the application
@@ -276,7 +302,7 @@ int call_usermodehelper_keys(char *path,
struct subprocess_info *sub_info;
int retval;

- if (!khelper_wq)
+ if (!khelper_wq || usermodehelper_disabled)
return -EBUSY;

if (path[0] == '\0')
@@ -319,7 +345,7 @@ int call_usermodehelper_pipe(char *path,
};
struct file *f;

- if (!khelper_wq)
+ if (!khelper_wq || usermodehelper_disabled)
return -EBUSY;

if (path[0] == '\0')
@@ -347,4 +373,5 @@ void __init usermodehelper_init(void)
{
khelper_wq = create_singlethread_workqueue("khelper");
BUG_ON(!khelper_wq);
+ pm_notifier(usermodehelper_pm_callback, 0);
}
-
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